[Mesa-dev] [PATCH 2/2] gallium: Add renderonly-based support for pl111+vc4.

[Emil Velikov]

On 19 May 2017 at 23:21, Eric Anholt <eric at anholt.net> wrote:
> Emil Velikov <emil.l.velikov at gmail.com> writes:
>
>> On 17 May 2017 at 20:13, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>> On 17 May 2017 at 18:53, Eric Anholt <eric at anholt.net> wrote:
>>>> Emil Velikov <emil.l.velikov at gmail.com> writes:
>>>>
>>>>> Hi Eric,
>>>>>
>>>>> On 11 May 2017 at 00:06, Eric Anholt <eric at anholt.net> wrote:
>>>>>> This follows the model of imx (display) and etnaviv (render): pl111 is a
>>>>>> display-only device, so when asked to do GL for it, we see if we have a
>>>>>> vc4 renderer, make the vc4 screen, and have vc4 call back to pl111 to do
>>>>>> scanout allocations.
>>>>>>
>>>>>> The difference from etnaviv is that we share the same BO between vc4 and
>>>>>> pl111, rather than having a vc4 bo and a pl11 bo and copies between the
>>>>>> two.  The only mismatch between their requirements is that vc4 requires
>>>>>> 4-pixel (at 32bpp) stride alignment, while pl111 requires that stride
>>>>>> match width.  The kernel will reject any modesets to an incorrect stride,
>>>>>> so the 3D driver doesn't need to worry about that.
>>>>>> ---
>>>>> I'm not familiar with the hardware itself so I cannot comment on those.
>>>>> There's a couple of small notes within, but overall the patch looks good.
>>>>>
>>>>>>  .travis.yml                                        |  2 +-
>>>>>>  Makefile.am                                        |  2 +-
>>>>> Yes, thank you!
>>>>>
>>>>>
>>>>>> --- a/Android.mk
>>>>>> +++ b/Android.mk
>>>>>
>>>>>>  classic_drivers := i915 i965
>>>>>> -gallium_drivers := swrast freedreno i915g nouveau r300g r600g radeonsi vmwgfx vc4 virgl
>>>>>> +gallium_drivers := swrast freedreno i915g nouveau pl111 r300g r600g radeonsi vmwgfx vc4 virgl
>>>>>>
>>>>> The recent Android cleanups by RobH which will cause a clash. The gist
>>>>> is below, but feel free to skim through commit
>>>>> 3f097396a1642bb7033002d0bdd37e194afce06a.
>>>>>  - rework for the new gallium_drivers format
>>>>>  - add a couple of lines in src/gallium/drivers/pl111/Android.mk
>>>>> analogous to the vc4 - the "ifneq $HAVE_foo" hunk
>>>>>  - drop the guard in src/gallium/Android.mk
>>>>>
>>>>>
>>>>>> +++ b/src/gallium/winsys/pl111/drm/pl111_drm_winsys.c
>>>>>
>>>>>> -#include <unistd.h>
>>>>>>  #include <fcntl.h>
>>>>>> +#include <unistd.h>
>>>>>>
>>>>>> -#include "vc4_drm_public.h"
>>>>>> +#include "pl111_drm_public.h"
>>>>>> +#include "vc4/drm/vc4_drm_public.h"
>>>>>> +#include "xf86drm.h"
>>>>>>
>>>>>> -#include "vc4/vc4_screen.h"
>>>>>> +#include "pipe/p_screen.h"
>>>>>> +#include "renderonly/renderonly.h"
>>>>>
>>>>>> +#include "util/u_format.h"
>>>>> Seems unused.
>>>>>
>>>>>>
>>>>>> -struct pipe_screen *
>>>>>> -vc4_drm_screen_create(int fd)
>>>>>> +struct pipe_screen *pl111_drm_screen_create(int fd)
>>>>>>  {
>>>>>> -       return vc4_screen_create(fcntl(fd, F_DUPFD_CLOEXEC, 3));
>>>>>> +   struct renderonly ro = {
>>>>>> +      /* Passes the vc4-allocated BO through to the pl111 DRM device using
>>>>>> +       * PRIME buffer sharing.  The VC4 BO must be linear, which the SCANOUT
>>>>>> +       * flag on allocation will have ensured.
>>>>>> +       */
>>>>>> +      .create_for_resource = renderonly_create_gpu_import_for_resource,
>>>>>> +      .kms_fd = fd,
>>>>>> +      .gpu_fd = drmOpenWithType("vc4", NULL, DRM_NODE_RENDER),
>>>>> Please don't use the drmOpen* API. It's a legacy dragon with very
>>>>> subtle and inner workings.
>>>>> Using drmGetDevice[s] should provide any information that you need.
>>>>> Alternatively please let us know what's missing so we can address it.
>>>>
>>>> One this platform, there are exactly two devices, one is vc4 and the
>>>> other is pl111.  drmOpenWithType is exactly the API we want, and if you
>>>> want something else, then you should probably replace its insides
>>>> instead of telling people to use a different API.
>>>
>>> Changing the insides also changes the behaviour, which could break users :-\
>>>
>> A couple of things from our IRC chat last night:
>>
>> - My suggestion was never meant as requirement or a blocker. Let along
>> "exerting control" as you call it :-\
>> It's aimed to save you/others time since the drmOpen* API
>> implementation is aimed for UMS and broken for KMS drivers.
>>
>> - You asked a couple of times "how this can break", despite my pointer
>> to DanielV's summary [1] and some encouragement to skim through the
>> drmOpen* code yourself.
>> Now a bit less tired, here it is the exact scenario how/why things are broken.
>>
>> A) User opens the vc4 device and calls drmSetInterfaceVersion
>> effectively populating the "unique name"
>> Plymouth, modesetting ddx, Xserver itself and others can easily do so.
>> B) Consecutive calls to  drmOpenWithType("vc4", NULL..) will fail
>> since the drmGetBusid/GET_UNIQUE return the non-zero "unique name".
>> That happens in drmOpenByName which considers the latter as "device
>> already opened".
>
> According to LIBGL_DEBUG=verbose, drmGetBusid is returning NULL on this
> platform.  drm_getunique() is banned on render nodes, resulting in an
> EACCES and drmGetBusid returns NULL.
>
Yes, SET_VERSION is not allowed for render nodes.

Have you tried opening the master vc4 node, calling the
drmSetInterfaceVersion and attempting drmOpen...?
If I'm not misreading the drm_file::master specifics, unique will be
set and drmOpen... will fail.

-Emil